CN112530724A - Method for manufacturing electron beam welding copper-tungsten contact piece by using tungsten powder - Google Patents
Method for manufacturing electron beam welding copper-tungsten contact piece by using tungsten powder Download PDFInfo
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- CN112530724A CN112530724A CN202011120337.8A CN202011120337A CN112530724A CN 112530724 A CN112530724 A CN 112530724A CN 202011120337 A CN202011120337 A CN 202011120337A CN 112530724 A CN112530724 A CN 112530724A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H11/00—Apparatus or processes specially adapted for the manufacture of electric switches
- H01H11/04—Apparatus or processes specially adapted for the manufacture of electric switches of switch contacts
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H11/00—Apparatus or processes specially adapted for the manufacture of electric switches
- H01H11/04—Apparatus or processes specially adapted for the manufacture of electric switches of switch contacts
- H01H11/048—Apparatus or processes specially adapted for the manufacture of electric switches of switch contacts by powder-metallurgical processes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H11/00—Apparatus or processes specially adapted for the manufacture of electric switches
- H01H11/04—Apparatus or processes specially adapted for the manufacture of electric switches of switch contacts
- H01H11/06—Fixing of contacts to carrier ; Fixing of contacts to insulating carrier
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/25—Process efficiency
Abstract
The invention discloses a method for manufacturing an electron beam welding copper-tungsten contact piece by using tungsten powder, which comprises the steps of S1 powder mixing, S2 forming, S3 skeleton firing, S4 sintering, S5 milling and S6 electron beam welding.
Description
Technical Field
The invention relates to the technical field of copper-tungsten contact piece manufacturing, in particular to a method for manufacturing an electron beam welding copper-tungsten contact piece by using tungsten powder.
Background
The copper-tungsten alloy material has high voltage resistance and arc ablation resistance, is widely applied to various switch arc contacts, and is the most widely applied contact material in various switches at present. The traditional production process uses a vacuum furnace or an atmosphere protection furnace for sintering copper infiltration, a heating body generates heat and then heats a workpiece in a heat conduction and convection mode, the whole hearth is heated, the energy consumption is higher, the production period is longer, the appearance of a sintered blank material is not in specification, the blank material allowance is larger, the material utilization rate is low, and the later-stage processing efficiency is reduced.
In addition, because the copper-tungsten alloy product has requirements on hardness, metal chromium needs to be added in the production process to improve the hardness of the product to more than 70HB, but after chromium is added, the precipitation of chromium element in the sintering process can affect the strength of a sintering joint surface (namely the joint part of the copper-tungsten alloy and the copper-chromium alloy), and the strength is gradually reduced along with the increase of the content of precipitated chromium, so that excessive chromium cannot be added, and the hardness improvement is limited.
Therefore, a novel manufacturing method using an electron beam as a heat source for welding is needed, a tungsten powder and copper powder mixing process is omitted, the method is suitable for preparing copper-tungsten alloys with different mass fraction ratios in small batches, the influence of chromium element precipitation on the hardness of the copper-tungsten alloys can be avoided, the welding blank is guaranteed to be regular in appearance, the machining efficiency is improved, the application range of the copper-tungsten contact is wider, and market demands are met.
Disclosure of Invention
The invention provides a method for manufacturing electron beam welding copper-tungsten contact plates by using tungsten powder.
The technical scheme of the invention is as follows: a method for manufacturing electron beam welding copper-tungsten contact pieces by using tungsten powder comprises the following steps:
s1 powder mixing: taking a proper amount of tungsten powder for pretreatment, adding the pretreated tungsten powder into an adhesive for mixing to obtain tungsten skeleton powder;
s2 forming: pressing the mixed tungsten skeleton powder on a press to obtain the tungsten skeleton powder with the density of 10.2-10.9g/cm3The tungsten blank of (2);
s3 baking framework: sintering the obtained tungsten blank in a high-temperature sintering furnace to a preset temperature, preserving heat for 3 hours, and cooling along with the furnace to obtain a tungsten framework;
s4 sintering: sintering and infiltrating pure copper and copper-chromium alloy on a tungsten framework to obtain fused contact end alloy, and preparing base end alloy with 1% chromium in a base end;
s5 milling: placing the sintered contact end alloy into a milling machine for milling;
s6 electron beam welding: and (3) arranging the prepared and milled contact end alloy and matrix end alloy in a special tool in a straight line, putting the special tool into electron beam equipment, and carrying out electron beam welding on the contact end alloy and the matrix end alloy.
Further, the step S1 of mixing the powder includes the following steps:
s1-1 pretreatment: reducing tungsten powder with the particle size of 4-10 mu m for 1h under the protection of reducing atmosphere at the temperature of 450-600 ℃ to obtain tungsten powder with surface activity;
s1-2 mixing: adding the tungsten powder obtained in the step S11 into a binder, and fully stirring and mixing the mixture under the vacuum condition of the temperature of 65-75 ℃, wherein the mixing time is 8-16h, the components of the binder are an oil-based binder and a paraffin-based binder, the mass ratio of the oil-based binder to the paraffin-based binder is 100:55, and the mass ratio of the binder to the tungsten powder is 1-5: 100.
Further, the pressing in the step S2 is a one-way pressing by a hydraulic oil press of 200 tons, and the pressing is more uniform.
Further, in the step S3, the temperature is first raised to 550-600 ℃ for preheating and dewaxing, the wax on the surface of the tungsten blank is removed, and then the temperature is raised to 1480-1520 ℃ for firing the tungsten framework.
Further, the step S4 of sintering, infiltrating, and infiltrating pure copper and copper-chromium alloy to obtain the fused contact end alloy specifically comprises the following steps:
s4-1: placing a sintered tungsten framework on one side of the bottom of a graphite crucible, placing a nickel alloy sheet with the same height as the tungsten framework on one side of the tungsten framework, wherein the thickness of the nickel alloy sheet is 0.2-0.5mm, a plurality of small holes are formed in the nickel alloy sheet, and placing a copper-chromium alloy prefabricated to contain 0.3-0.7 wt% of chromium on one side of the nickel alloy sheet;
s4-2: placing a nickel alloy sheet on one side above a tungsten framework, placing the copper-chromium alloy above the nickel alloy sheet, wherein the width of the nickel alloy sheet is equal to that of the copper-chromium alloy;
s4-3: placing a nickel alloy sheet above the copper-chromium alloy on one side of the tungsten framework, placing feeding T1 pure copper above the nickel alloy sheet, forming a reserved space between the nickel alloy sheet and the tungsten framework, infiltrating the copper-chromium alloy and the feeding T1 pure copper, enabling the nickel alloy sheet to fall, and then placing the graphite crucible into a continuous boat pushing furnace for vacuum sintering;
s4-4: the temperature is raised to 1090-1100 ℃ for primary sintering, the temperature is higher than the melting point of copper 1083.4 ℃, so that two pieces of copper-chromium alloy are melted and permeate into the tungsten framework along the small hole and the reserved space, feeding T1 pure copper is melted and permeate into the tungsten framework along the small hole for 3 hours, a fused copper-tungsten contact is obtained, and the uppermost nickel alloy sheet falls to the upper part of the tungsten framework;
s4-5: then, the temperature is raised to 1320-1380 ℃ for secondary sintering, the temperature is higher than the melting point of the nickel alloy sheet 1312.8 ℃, the temperature is lower than the melting point of the tungsten framework 1460-1520 ℃ so as not to melt the tungsten framework, the nickel alloy sheet is melted to be used as a welding flux for welding a gap between the copper-tungsten contact and the molten copper alloy which is not infiltrated, so that chromium elements precipitated from the copper-chromium alloy are infiltrated into a welding seam and lasts for 3 hours to obtain a contact end alloy, the strength of the joint part of the copper-tungsten alloy and the copper is obviously increased, and the hardness is enough to meet the use requirement;
s4-6: cooling and discharging.
Further, in the step S4-3, the copper content of the feeding T1 pure copper is more than 99.95 wt%, and the nickel alloy sheet has the composition of Ni: 81-88%, P: 3-8%, Ag: 2-5%, Cu: 0.8-3%, Zn: 0.3-2%, Sn: 0.3-2%, Nb: 0.05-0.4%, and the hardness and the conductivity both meet the use requirements.
Further, the step S5 of milling specifically includes:
s5-1: mounting the sintered contact end alloy on a milling machine by using a graphite milling cutter with the diameter
The rotating speed is 180-The cutting depth is 2-3 mm;
s5-2: and connecting the anode and the cathode of a power supply with the milling cutter and the sintered contact end alloy respectively, wherein the sintered contact end alloy can move along the surface parallel to the milling machine, adjusting the discharge gap, and turning on a pulse power supply to perform discharge washing and cutting processing, wherein the pulse period of the pulse power supply is 660-plus-890 us, and the current is 900-plus-1000A.
Furthermore, in the step S5-2, when the two side surfaces corresponding to the right-angled edges of the copper-tungsten contact of the contact end alloy are machined, a conductive fluid is coated on the surface of the graphite milling cutter in advance, the conductive fluid is solidified to form a conductive fluid solidified layer with a melting point higher than that of the copper-tungsten contact, the pulse power supply is turned on to enable the conductive fluid solidified layer to perform discharge milling on the two side surfaces of the copper-tungsten contact, the milling depth is adjusted to be 1.5-2mm, the conductive fluid is continuously supplemented during the machining to compensate the conductive fluid solidified layer eroded by the electric spark, self-repairing is achieved, and the milling depth is controlled to avoid the loss performance of the contact end due to over-deep milling.
Further, the step S6 is performed in a vacuum environment when the vacuum degree reaches 4.6 × 10-2Setting the beam spot of the electron beam welding seam into a circle, adjusting the surface focusing value, setting the cladding voltage of 60kV, the beam current of 60-70mA, the scanning defocusing value of 0-12J, the speed of 300-2And the single-class welding quantity is more than 110 pieces, the processing efficiency of finished products is obviously improved, and the utilization rate of raw materials is high.
The invention has the beneficial effects that:
(1) the invention changes the traditional production mode, adopts the electron beam welding mode to connect the contact end and the matrix end, and only sinters and welds the required copper layer at the contact end, thereby reducing the size specification of the copper-tungsten alloy end, improving the furnace charge, and the welding blank has regular appearance and higher strength than the integral sintered piece.
(2) The welding process is designed according to the structure of the contact piece product, the base end is made of chromium and copper with 1% of chromium content, the hardness is enough to meet the use requirement, the contact end is made of chromium and copper with 0.3-0.7% of chromium content, and the hardness and the electrical conductivity after welding meet the product requirement.
(3) According to the invention, the electron beam welding line is designed in the product clamping groove, the defects of the sharp corner position of the welding line are completely machined in the later stage, the welding allowance does not need to be additionally increased, the raw material investment is less, the utilization rate is high, the welding blank is more regular, and the machining efficiency of the finished product in the later stage is greatly improved.
Drawings
FIG. 1 is a schematic diagram of the sintering structure of step S4 of the present invention;
FIG. 2 is a front view of the sintering of step S4 of the present invention;
FIG. 3 is a top plan view of the sintering of step S4 of the present invention;
FIG. 4 is a schematic structural view of the contact end alloy and the matrix end alloy after step S5 of the present invention is milled;
FIG. 5 is a schematic view of an electron beam welding configuration of step S6 of the present invention;
FIG. 6 is a pictorial view of step S6 of electron beam welding of the present invention;
FIG. 7 is a pictorial view of a master object manufactured using the method of the present invention;
FIG. 8 is a pictorial view of a copper-tungsten wafer fabricated by slicing a master part made by the method of the present invention;
fig. 9 is a schematic diagram of the strength test of the copper-tungsten contact in embodiment 1 of the present invention.
The welding method comprises the following steps of 1-tungsten framework, 2-graphite crucible, 3-copper-chromium alloy, 4-feeding T1 pure copper, 5-nickel alloy sheet, 51-small hole, 6-copper-tungsten contact, 7-contact end alloy, 8-matrix end alloy and 9-electron beam welding line.
Detailed Description
Example 1
A method for manufacturing electron beam welding copper-tungsten contact pieces by using tungsten powder comprises the following steps:
s1 powder mixing: taking a proper amount of tungsten powder for pretreatment, adding the pretreated tungsten powder into an adhesive for mixing to obtain tungsten skeleton powder; the method comprises the following specific steps:
s1-1 pretreatment: reducing tungsten powder with the particle size of 8.5 microns for 1h under the protection of reducing atmosphere at 550 ℃ to obtain tungsten powder with surface activity;
s1-2 mixing: adding the tungsten powder obtained in the step S11 into an adhesive, and fully stirring and mixing the mixture under the vacuum condition of the temperature of 66 ℃, wherein the mixing time is 12 hours, the adhesive comprises an oil-based adhesive and a paraffin-based adhesive, the mass ratio of the oil-based adhesive to the paraffin-based adhesive is 100:55, and the mass ratio of the adhesive to the tungsten powder is 3.5: 100;
s2 forming: the mixed tungsten skeleton powder is pressed on a 200 ton hydraulic oil press in a single direction to form the tungsten skeleton powder with the density of 10.5g/cm3The tungsten blank of (2);
s3 baking framework: firstly, sintering the obtained tungsten blank in a high-temperature sintering furnace to 590 ℃, preheating and dewaxing, removing wax on the surface of the tungsten blank, then heating to 1505 ℃, sintering the tungsten framework 1, preserving heat for 3 hours, and cooling along with the furnace to obtain the tungsten framework 1;
s4 sintering: as shown in fig. 1, pure copper and copper-chromium alloy are sintered and infiltrated on a tungsten framework 1 to obtain a fused contact end alloy 7, as shown in fig. 4, a matrix end alloy 8 with a matrix end containing 1% of chromium is prepared at the same time, and the method comprises the following specific steps:
s4-1: as shown in fig. 2 and 3, a sintered tungsten skeleton 1 is placed on one side of the bottom of a graphite crucible 2, and a copper-chromium alloy 3 which is prepared and contains 0.5 wt% of chromium is placed on one side of the tungsten skeleton 1;
s4-2: placing a copper-chromium alloy 3 above the tungsten framework 1 and close to one side of the graphite crucible;
s4-3: placing feeding T1 pure copper 4 above the copper-chromium alloy 3 on one side of the tungsten framework 1, wherein the copper content of the feeding T1 pure copper 4 is 99.96 wt%, and a reserved space is formed between the feeding T1 pure copper 4 and the tungsten framework 1 and is used for infiltration of the copper-chromium alloy 3 and the feeding T1 pure copper 4, and then placing the graphite crucible 2 into a continuous push boat furnace for vacuum sintering, wherein the continuous push boat furnace is a commercially available American imported high-temperature BTU automatic continuous push boat furnace;
s4-4: heating to 1300 ℃ for sintering, wherein the temperature is higher than the melting point of copper of 1083.4 ℃, the melting point of the tungsten framework is lower than the melting point of the tungsten framework, so that the tungsten framework is not melted, two pieces of copper-chromium alloy 3 are melted and penetrate into the tungsten framework 1 along the reserved space, and feeding T1 pure copper 4 is melted and penetrates into the tungsten framework 1 for 3 hours to obtain a fused copper-tungsten contact 6;
s4-5: cooling and discharging;
s5 milling: placing the sintered contact end alloy 7 into a milling machine for match milling, wherein the matrix end alloy 8 is a standard part, and the match milling is not needed in the die forming;
s6 electron beam welding: as shown in fig. 5 and 6, the milled contact end alloy 7 and the milled base end alloy 8 are arranged in a line on a special tool, and are put into an electron beam device, the contact end alloy 7 and the base end alloy 8 are subjected to electron beam welding, and the step S6 is performed under a vacuum environment when the vacuum degree reaches 4.6 × 10-2Setting the beam spot of the electron beam welding seam 9 into a circular shape, adjusting the surface focus value, setting the cladding voltage 60kV, the beam current 65mA, the scanning defocusing value 12J, the speed 330mm/min, and the beam spot energy 107W/cm2And cutting the welded copper-tungsten alloy into pieces to obtain the copper-tungsten alloy contact piece, wherein the welding amount of one work is 120 pieces, and the welded copper-tungsten alloy contact piece is shown in figures 7 and 8.
Example 2
This embodiment is substantially the same as embodiment 1 except that:
step S2 forming: the mixed tungsten skeleton powder is pressed on a 200 ton hydraulic oil press in a single direction to form the tungsten skeleton powder with the density of 10.2g/cm3The tungsten blank of (2);
example 3
This embodiment is substantially the same as embodiment 1 except that:
step S2 forming: the mixed tungsten skeleton powder is pressed on a 200 ton hydraulic oil press in a single direction to form the tungsten skeleton powder with the density of 10.9g/cm3The tungsten blank of (2);
example 4
This embodiment is substantially the same as embodiment 1 except that:
the chromium-copper alloy 3 used in step S41 is a chromium-copper alloy containing 0.3 wt% of chromium;
example 5
This embodiment is substantially the same as embodiment 1 except that:
the chromium-copper alloy 3 used in step S41 was a chromium-copper alloy containing 0.7 wt% chromium;
example 6
This embodiment is substantially the same as embodiment 1 except that:
s4 sintering: as shown in fig. 1, pure copper and copper-chromium alloy are sintered and infiltrated on a tungsten framework 1 to obtain a fused contact end alloy 7, as shown in fig. 4, a matrix end alloy 8 with a matrix end containing 1% of chromium is prepared at the same time, and the method comprises the following specific steps:
s4-1: as shown in fig. 2 and 3, the fired tungsten skeleton 1 is placed on the bottom side of the graphite crucible 2, a nickel alloy sheet 5 having the same height as the tungsten skeleton 1 is placed on the tungsten skeleton 1 side, the thickness of the nickel alloy sheet 5 is 0.3mm, and the nickel alloy sheet 5 has the following components: 83%, P: 7%, Ag: 4.5%, Cu: 2.2%, Zn: 1.7%, Sn: 1.4%, Nb: 0.2 percent of the chromium-containing copper-chromium alloy sheet 5 is provided with a plurality of small holes 51, and the copper-chromium alloy 3 with 0.5 percent of chromium is prefabricated and placed on one side of the nickel alloy sheet 5;
s4-2: a nickel alloy sheet 5 is placed on one side above the tungsten framework 1, a copper-chromium alloy 3 is placed above the nickel alloy sheet 5, and the width of the nickel alloy sheet 5 is equal to that of the copper-chromium alloy 3;
s4-3: placing a nickel alloy sheet 5 above the copper-chromium alloy 3 on one side of the tungsten framework 1, placing feeding T1 pure copper 4 above the nickel alloy sheet 5, wherein the copper content of the feeding T1 pure copper 4 is 99.97%, and a reserved space is formed between the nickel alloy sheet 5 and the tungsten framework 1 and is used for infiltration of the copper-chromium alloy 3 and the feeding T1 pure copper 4 and falling of the nickel alloy sheet 5, and then placing the graphite crucible 2 into a continuous boat pushing furnace for vacuum sintering in a vacuumizing manner, wherein the continuous boat pushing furnace is a commercially available American imported high-temperature BTU automatic continuous boat pushing furnace;
s4-4: heating to 1090 ℃ for primary sintering, wherein the temperature is higher than the melting point of copper 1083.4 ℃, so that two pieces of copper-chromium alloy 3 are melted and penetrate into the tungsten framework 1 along the small hole 51 and the reserved space, feeding T1 pure copper 4 is melted and penetrates into the tungsten framework 1 along the small hole 51, the melting lasts for 3 hours, a fused copper-tungsten contact 6 is obtained, and the uppermost nickel alloy sheet 5 falls to the position above the tungsten framework 1;
s4-5: heating to 1380 ℃ for secondary sintering, wherein the temperature is higher than the melting point of the nickel alloy sheet of 1312.8 ℃, the melting point of the tungsten skeleton is lower than the melting point of the tungsten skeleton, the tungsten skeleton is not melted, the nickel alloy sheet 5 is melted to be used as a welding flux for welding a gap between the copper-tungsten contact 6 and the molten copper alloy which is not infiltrated, chromium elements separated out from the copper-chromium alloy 3 are infiltrated into a welding line, and the welding line lasts for 3 hours, so that a contact end alloy 7 is obtained;
s4-6: cooling and discharging.
Example 7
This embodiment is substantially the same as embodiment 6 except that:
the thickness of the nickel alloy sheet 5 used in step S41 was 0.5mm, and the composition of the nickel alloy sheet 5 was Ni: 88%, P: 5%, Ag: 4%, Cu: 1%, Zn: 0.8%, Sn: 0.8%, Nb: 0.4 percent;
example 8
This embodiment is substantially the same as embodiment 6 except that:
s5 milling: placing the sintered contact end alloy 7 and the sintered matrix end alloy 8 into a milling machine for milling;
s5-1: mounting the sintered contact end alloy 7 on a milling machine, and adopting a milling cutter made of graphite material with the melting point far higher than that of copper-tungsten alloy, wherein the diameter of the milling cutter
The rotating speed is 240r/min, the feeding speed is 300mm/min, and the milling depth is adjusted to be 2.5 mm;
s5-2: connecting the anode and the cathode of a power supply with a milling cutter and a sintered contact end alloy 7 respectively, wherein the sintered contact end alloy 7 can move along the surface parallel to the milling machine, adjusting a discharge gap, and turning on a pulse power supply for discharge washing and cutting, wherein the pulse period of the pulse power supply is 800us, and the current is 950A;
when the conductive fluid is machined to the two side faces corresponding to the right-angle edges of the copper-tungsten contact 6 of the contact end alloy 7, coating the conductive fluid on the surface of the graphite milling cutter in advance, solidifying the conductive fluid to form a conductive fluid solidified layer with a melting point higher than that of the copper-tungsten contact 6, turning on a pulse power supply to enable the conductive fluid solidified layer to perform discharge milling on the two side faces of the copper-tungsten contact 6, adjusting the milling depth to be 1.5mm, continuously supplementing the conductive fluid during machining to compensate the conductive fluid solidified layer eroded by electric sparks, and realizing self-repairing, wherein the conductive fluid is conductive ink sold in the market.
Example 9
The embodiment comprises the following steps:
s1 powder mixing: taking a proper amount of tungsten powder for pretreatment, and adding an adhesive into the treated tungsten powder for mixing; the method comprises the following specific steps:
s1-1 pretreatment: reducing tungsten powder with the particle size of 8.5 microns for 1h under the protection of reducing atmosphere at 550 ℃ to obtain tungsten powder with surface activity;
s1-2 mixing: and (3) adding the tungsten powder obtained in the step (S11) into a binder, and fully stirring and mixing the mixture at the temperature of 66 ℃ under vacuum for 12h, wherein the binder comprises an oil-based binder and a paraffin-based binder in a mass ratio of 100:55, and the mass ratio of the binder to the tungsten powder is 3: 100.
S2 forming: the mixed tungsten skeleton powder is pressed on a 200 ton hydraulic oil press in a single direction to form the tungsten skeleton powder with the density of 10.5g/cm3The tungsten blank of (2);
s3 baking framework: firstly, sintering the obtained tungsten blank in a high-temperature sintering furnace to 590 ℃, preheating and dewaxing, removing wax on the surface of the tungsten blank, then heating to 1505 ℃, sintering the tungsten framework 1, preserving heat for 3 hours, and cooling along with the furnace to obtain the tungsten framework 1;
s4 sintering: and (3) integrally sintering and infiltrating copper and the copper-chromium alloy on the tungsten framework 1 to obtain the fused copper-tungsten alloy contact.
Experimental example 1: study of the influence of tungsten frameworks 1 of different densities on the properties of the finished product
The copper-tungsten contact wafers prepared in examples 1-3 were tested for performance according to the following test methods:
1. as shown in FIG. 9, according to GB/T21143-2014, unified test method for quasi-static fracture toughness of metal materials, a copper-tungsten contact piece is placed on a CMT5205 electronic universal tester for testing, the tensile rate is 5mm/mnin, and the tensile strength of the copper-tungsten alloy is measured.
2. According to GB/T230.1-2018 part 1 of Rockwell hardness test of metal materials: the hardness of the copper-tungsten contact piece is tested according to the standard of test method, a 50 kg load is adopted to place a flat ground sample on a workbench, the focus is adjusted, the indentation is punched, and the diagonal length is read to obtain the hardness value.
3. And (3) testing the conductivity of the copper-tungsten contact piece by using an FQR7501 eddy current conductivity meter according to GB/T11007-2008 conductivity meter test method.
The test results are shown in table 1:
table 1 performance test results for copper tungsten contacts prepared in examples 1-3
And (4) conclusion: it can be seen from table 1 that, in comparative examples 1-3, under the condition of the same process steps and different tungsten skeleton densities, the tungsten skeleton density is higher, the tensile strength is stronger, but the hardness and the conductivity are lower, so that a tungsten blank with lower tungsten skeleton density is prepared under the condition of meeting a certain tensile strength, and when the tensile strength requirement of a workpiece is more than or equal to 300MPa, the copper-tungsten contact piece prepared in example 2 has the optimal performance.
Experimental example 2: study of the Effect of copper-chromium alloy 3 with different chromium contents on the Properties of the finished products
The copper-tungsten contact wafers prepared in examples 1, 4 and 5 were subjected to the performance test in the same manner as in example 1, and the test results are shown in table 2:
table 2 performance test results for copper tungsten contacts prepared in examples 1, 4, 5
And (4) conclusion: it can be seen from table 2 comparing examples 1, 4, and 5 that under the condition of different chromium contents in the copper-chromium alloy 3 added in the same process steps, the higher the chromium content in the copper-tungsten alloy is, the hardness is obviously increased, and the change of the electrical conductivity is not obvious, because the precipitation of chromium element in the sintering process affects the tensile strength of the sintering joint surface (i.e. the joint portion of the copper-tungsten alloy and the copper-chromium alloy), and the increase of chromium content increases the tensile strength to some extent, but because the added nickel alloy piece 5 is used as a solder to play a connecting role, the influence of the precipitation of chromium element on the sintering joint surface is reduced, the decrease of the tensile strength is smaller, and the performance of the copper-tungsten contact piece prepared in example 5 is optimal.
Experimental example 3: study on the influence of nickel alloy sheets 5 with different nickel contents on the properties of the finished product
The copper-tungsten contact wafers prepared in examples 1, 6 and 7 were subjected to the performance test in the same manner as in example 1, and the test results are shown in table 3:
table 3 performance test results for copper tungsten contacts prepared in examples 1, 6, 7
And (4) conclusion: it can be seen from table 3 comparing examples 1, 6, and 7 that when the sintering process is performed by changing the process step S4, the copper-tungsten contact sheet with the nickel sheet added thereto has improved properties, and the nickel content in the nickel alloy sheet is different, and the tensile strength and hardness are increased to some extent with the increase of the nickel content, but the conductivity is reduced, so the nickel content in the nickel alloy sheet is not too high, and the copper-tungsten contact sheet prepared in example 6 has the best properties.
Experimental example 4: research on influence of different milling modes on performance of finished products
The copper-tungsten contact pieces prepared in examples 6 and 8 were subjected to the performance test in the same manner as in example 1, and the test results are shown in table 4:
table 4 performance test results for copper tungsten contacts prepared in examples 6 and 8
And (4) conclusion: it can be seen from table 4 comparing examples 6 and 8 that the loss of tensile strength and hardness after match milling in example 8 is reduced compared with example 6, so when the workpiece after machining is match milled by adopting the pulsed fluidized match milling method, the milling depth can be controlled to avoid the loss performance of the contact end caused by too deep milling.
Experimental example 5: research on the utilization rate difference of copper-tungsten contact piece materials obtained by electron beam welding and integral sintering
The materials for the copper-tungsten contact pads prepared in examples 1 and 9 are shown in table 5:
table 5 use of copper tungsten contact stock prepared in examples 1 and 9
And (4) conclusion: by comparison in Table 5, the raw material utilization rate was 19.81% based on the total sintered raw material input and the weight of the finished product; when the electron beam welding process is used, the occupied space is small, the whole furnace loading amount is doubled, the welded copper-tungsten contact piece is molded by a standard piece mold, and the comprehensive material utilization rate is improved to 34.5%.
Claims (9)
1. A method for manufacturing an electron beam welding copper-tungsten contact piece by using tungsten powder is characterized by comprising the following steps:
s1 powder mixing: taking a proper amount of tungsten powder for pretreatment, adding the pretreated tungsten powder into an adhesive for mixing to obtain tungsten skeleton powder;
s2 forming: pressing the mixed tungsten skeleton powder on a press to obtain the tungsten skeleton powder with the density of 10.2-10.9g/cm3The tungsten blank of (2);
s3 baking framework: sintering the obtained tungsten blank in a high-temperature sintering furnace to a preset temperature, preserving heat for 3 hours, and cooling along with the furnace to obtain a tungsten framework (1);
s4 sintering: sintering and infiltrating pure copper and copper-chromium alloy on a tungsten framework (1) to obtain a fused contact end alloy (7), and preparing a base end alloy (8) containing 1% of chromium;
s5 milling: placing the sintered contact end alloy (7) into a milling machine for milling;
s6 electron beam welding: and (3) opening the prepared contact end alloy (7) and the matrix end alloy (8) into electron beam equipment in a straight line for electron beam welding.
2. The method of claim 1, wherein the step S1 of mixing the powder comprises the following steps:
s1-1 pretreatment: reducing tungsten powder with the particle size of 4-10 mu m for 1h under the protection of reducing atmosphere at the temperature of 450-600 ℃ to obtain tungsten powder with surface activity;
s1-2 mixing: adding the tungsten powder obtained in the step S11 into a binder, and fully stirring and mixing the mixture under the vacuum condition of the temperature of 65-75 ℃, wherein the mixing time is 8-16h, the components of the binder are an oil-based binder and a paraffin-based binder, the mass ratio of the oil-based binder to the paraffin-based binder is 100:55, and the mass ratio of the binder to the tungsten powder is 1-5: 100.
3. The method of claim 1, wherein the step of pressing in S2 is one-way pressing with a 200 ton hydraulic oil press.
4. The method as claimed in claim 1, wherein the step S3 comprises firing the tungsten skeleton (1) by raising the temperature to 550-600 ℃ for dewaxing, and raising the temperature to 1480-1520 ℃.
5. The method for manufacturing electron beam welding copper-tungsten contact blades by using tungsten powder as claimed in claim 1, wherein the step of sintering and infiltrating pure copper and copper-chromium alloy in the step of S4 to obtain the fused contact end alloy (7) comprises the following specific steps:
s4-1: placing a sintered tungsten framework (1) on one side of the bottom of a graphite crucible (2), placing a nickel alloy sheet (5) with the same height as the tungsten framework (1) on one side of the tungsten framework (1), wherein the thickness of the nickel alloy sheet (5) is 0.2-0.5mm, a plurality of small holes (51) are formed in the nickel alloy sheet (5), and placing a copper-chromium alloy (3) which is prefabricated and contains 0.3-0.7 wt% of chromium on one side of the nickel alloy sheet (5);
s4-2: a nickel alloy sheet (5) is placed on one side above a tungsten framework (1), the copper-chromium alloy (3) is placed above the nickel alloy sheet (5), and the width of the nickel alloy sheet (5) is equal to that of the copper-chromium alloy (3);
s4-3: placing a nickel alloy sheet (5) above the copper-chromium alloy (3) on one side of the tungsten framework (1), placing feeding T1 pure copper (4) above the nickel alloy sheet (5), forming a reserved space between the nickel alloy sheet (5) and the tungsten framework (1) for infiltration of the copper-chromium alloy (3) and the feeding T1 pure copper (4) and enabling the nickel alloy sheet (5) to fall, and then placing the graphite crucible (2) into a continuous boat pushing furnace for vacuum sintering;
s4-4: the temperature is raised to 1090-;
s4-5: then, the temperature is raised to 1320-1380 ℃ for secondary sintering, the nickel alloy sheet (5) is melted to be used as a welding flux for welding a gap between the copper-tungsten contact (6) and the molten copper alloy which is not infiltrated, so that chromium element precipitated from the copper-chromium alloy (3) is infiltrated into a welding line and lasts for 3 hours, and a contact end alloy (7) is obtained;
s4-6: cooling, discharging and preparing the base end alloy (8) containing 1% of chromium.
6. The method for manufacturing electron beam welding copper-tungsten contact pieces by using tungsten powder as claimed in claim 5, wherein the copper content of the feeding T1 pure copper (4) in the step S4-3 is more than 99.95 wt%, and the composition of the nickel alloy piece (5) is Ni: 81-88%, P: 3-8%, Ag: 2-5%, Cu: 0.8-3%, Zn: 0.3-2%, Sn: 0.3-2%, Nb: 0.05-0.4 percent.
7. The method for manufacturing electron beam welding copper-tungsten contact pieces by using tungsten powder as claimed in claim 1, wherein the step S5 is milling specifically:
s5-1: mounting the sintered contact end alloy (7) on a milling machine by using a milling cutter made of graphite material and having a diameter
The rotating speed is 180-;
s5-2: and connecting the anode and the cathode of a power supply with the milling cutter and the sintered contact end alloy (7) respectively, wherein the sintered contact end alloy (7) can move along the surface parallel to the milling machine, adjusting the discharge gap, and turning on a pulse power supply to perform discharge washing and cutting processing, wherein the pulse period of the pulse power supply is 660-plus 890us, and the current is 900-plus 1000A.
8. The method for manufacturing electron beam welded Cu-W contact strip using W powder as claimed in any one of claims 1-7, wherein in S5-2, when machining to two sides corresponding to the right-angled edges of the Cu-W contact (6) of the contact end alloy (7), the graphite milling cutter is coated with conductive fluid in advance, the conductive fluid is solidified to form a solidified layer of conductive fluid with melting point higher than that of the Cu-W contact (6), the pulse power supply is turned on to make the solidified layer of conductive fluid perform discharge milling on the two sides of the Cu-W contact (6), the milling depth is adjusted to 1.5-2mm, and the conductive fluid is continuously supplemented to compensate the solidified layer of conductive fluid eroded by the spark.
9. The method as claimed in claim 1, wherein the step S6 is performed in a vacuum environment when the vacuum degree reaches 4.6 x 10-2Adjusting parameters of beam blanking at Pa, setting the beam spot of the electron beam welding seam (9) into a circle, adjusting the surface focusing value, setting the cladding voltage of 60kV, the beam current of 60-70mA, the scanning defocusing value of 0-12J, the speed of 300-2The welding quantity of a single shift is more than 110 pieces.
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